1. Field of the Invention
The present invention relates to an apparatus for recognizing road configurations ahead of an own vehicle by identifying lane markers drawn on road surfaces.
2. Background Art
Recently, people have shown an interest in an apparatus for monitoring vehicle surroundings (hereinafter, referred to as vehicle surroundings monitoring apparatus) for recognizing road configurations in front of an own vehicle using a preview sensor such as monocular camera, stereoscopic camera and the like. In order to recognize the road configuration, it is important to detect lane markers (white markers, no passing lines and the like) drawn on road surfaces. In case where a monocular camera is used as a preview sensor, the detection of lane markers is performed only based on information of two-dimensional picture image, that is, brightness of image. However, the picture image obtained from the monocular camera does not provide distance information to an object. Accordingly, there is a possibility that objects having a brightness characteristic similar to lane markers, such as pillars of preceding vehicles, guardrails and the like, are recognized as lane markers.
On the other hand, in case where a stereoscopic camera is used in place of a monocular camera, it is possible to obtain distance information to objects from a pair of picture images. This is absolutely advantageous over the monocular camera. Japanese Patent Application Laid-open No. Toku-Kai-Hei 5-265547 discloses a technology in which a distance image (distribution characteristic of distance in picture images) is calculated based on a parallax in stereo images and objects (preceding vehicles, road surfaces and the like) are recognized only from the distance image.
In case where the lane markers are recognized only based on the distance image obtained from the stereo images, there is a possibility that objects having the configuration similar to lane markers and the different brightness characteristic are recognized as lane markers, because only rough configurations of objects are obtained from the distance distribution built in the distance image. Such objects, for example, are traces of tire slips, shades, patches and the like.
It is an object of the present invention to provide a lane recognition apparatus capable of recognizing the position of lane markers in the real space using both of the distance information obtained from a pair of picture images and the brightness information in the picture images. Further, it is another object of the present invention to enhance the reliability of the vehicle surroundings monitoring control by raising the accuracy of recognition of lane markers.
To achieve these objects, a lane recognition apparatus for recognizing lane markers on a road surface based on a pair of stereo images of a scene in front of an own vehicle obtained from a stereoscopic camera, comprises a stereo image processing means for calculating a distance information of an image based on the pair of the images, a lane detecting means for detecting a lane marker of a lane in the image based on a brightness information of the image and the distance information calculated by the stereo image processing means and a lane position recognition means for recognizing a position of the lane marker in real space based on a position of the lane marker detected by the lane detecting means and the distance information calculated by the stereo image processing means.